High voltage modular battery with electrically-insulated cell module and interconnector peripheries

ABSTRACT

A modular battery includes a housing, a first planar battery cell having a first planar electrode surface, a second planar battery cell having a second planar electrode surface, and an interconnector disposed between the first planar surface and the second planar surface and electrically connecting the first and second planar electrode surfaces, side peripheries of the interconnector, the first and second planar battery cells being electrically insulated from the housing. A method is also provided.

This is a continuation of U.S. application Ser. No. 12/650,814 filedDec. 31, 2009, which is hereby incorporated by reference herein, andclaims priority to U.S. Provisional Patent Application No. 61/214,743,filed Apr. 28, 2009 and hereby incorporated by reference herein.

BACKGROUND

Modular batteries are batteries which comprise two or more battery cellsor cell modules or cells. A common example of a device using a modularbattery is a hand held flashlight which may use for example two C cells.

Recently, modular batteries have become important in many applications,including hybrid electric vehicles (“HEV”), plug-in hybrid electricvehicles (“PHEV”), and other applications. When used in HEV, PHEV, andother applications, in addition to being durable, safe and costeffective, modular batteries are required to deliver a great deal ofpower.

Applications of modular batteries, like the hand-held flashlight,require the use of multiple battery cells connected in series. However,the modular batteries for HEVs and PHEVs, for example, may differ fromthe modular C cells used in a common flashlight.

U.S. Pat. Nos. 5,552,243 and 5,393,617 disclose a bipolarelectrochemical battery of stacked wafer cells. The wafer cells areelectrically connected in series with the positive face of each cellcontacting the negative face of the adjacent cell. The cell-to-cellcontact may be enhanced by use of a conductive paste or cement. Thestack assembly is held in compression. U.S. Pat. Nos. 5,552,243 and5,393,617 are hereby incorporated by reference herein.

SUMMARY OF THE INVENTION

The present invention provides a modular battery comprising a housing, afirst planar battery cell having a first planar electrode surface, asecond planar battery cell having a second planar electrode surface, andan interconnector disposed between the first planar surface and thesecond planar surface and electrically connecting the first and secondplanar electrode surfaces, side peripheries of the interconnector, thefirst and second planar battery cells being electrically insulated fromthe housing.

The present invention also provides a method for forming a modularbattery comprising: placing a first planar battery cell having a firstplanar electrode surface in a housing, placing an interconnector overthe first planar battery cell in the housing, placing a second planarbattery cell having a second planar electrode surface in the housing, sothat the interconnector electrically connects the first and secondplanar electrode surfaces and side peripheries of the interconnector,the first and second planar battery cells being electrically insulatedfrom the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with respect to a preferredembodiment, in which:

FIGS. 1A, 1B, 1C and 1D are plan views of four types of electrodes thatmay be used in the present invention;

FIG. 2 is a schematic cross section of the electrode arrangement withina single cell module with interleaving electrodes and separators;

FIG. 3A is a schematic front view of a sealed single cell showing thecell module with the front frame section removed, while FIG. 3B showsthe cell module with the front frame section in place, and both FIGS. 3Aand 3B showing placement of interconnectors according to the presentinvention;

FIG. 4 is a plan view of the cell module with an interconnector on topand showing the plastic frame with feedthroughs, burst disc and ports;

FIG. 5 is a perspective view of the plastic frame with communicatingfeedthroughs for filling, sealing and sensing;

FIG. 6A schematically illustrates a cross-section of a modular batteryhaving six cell modules within an enclosure with feedthroughs, whileFIG. 6B shows a plan view; while FIG. 6C shows the interconnector withan insulating side periphery; and

FIG. 7 is an explanatory view illustrating remote monitoring andalerting of the battery and its cell modules.

The drawings are schematic in nature and not to scale. For clarity andease of understanding, some elements have been exaggerated in size.

DETAILED DESCRIPTION

In order to be powerful enough for HEVs, PHEVs, and other applications,it is desirable to use modular batteries containing cells with a highsurface to volume ratio, for example using a planar design for each cellof the battery. These cells may be, for example, about the size of alarge book wherein the “front” of the book contains, for example, apositive terminal (also known as an electrode) and the “back” of thebook contains, for example, a negative terminal. Unlike theircylindrical counterparts (e.g., C cell batteries) which use a raiseddimple at one end of a cell to make electrical contact with the nextcylindrical cell, substantially planar cells need not have such raiseddimple(s).

For many applications requiring high electrical power including HEVs andPHEVs, it is desirable that the battery delivers electrical power at ahigh voltage in order to reduce the required current needed to supplythe electrical power which in turn will beneficially reduce the need forhigh-current carrying materials to the devices using the electricalpower. Electrical power is the multiple of voltage and current and highvoltage delivery of electrical power to a device, for example anelectric motor, will require thinner or less conductive current carriers(for example, copper wire) to the device which will reduce their cost.Electric vehicles, for example, may require a battery to provideelectrical power at 300 to 600 volts. This high voltage is typicallyachieved by externally connecting multiple lower voltage battery moduleselectrically in series. This is in part due to safety considerations inassembling and operating a series connected “stack” of typical “pouch”cells within a battery module, since at higher voltages and especiallyabove approximately 60 Volts, there is a significant risk of electricalarcing and a severe shock hazard since the edge peripheries of “flat”cells such as typical “pouch” cells have their cell terminals exposed.For safety these cell terminals are connected electrically in serieswithin a low voltage battery module, for example, having less than 60volts.

An object of the present invention is to provide interconnectors andcell modules each with electrically-insulating peripheries to protectagainst accidental electrical arcing and during assembly and operationof a multi-celled high voltage battery where only the battery endterminations are exposed. A single battery module of the presentinvention could contain up to a hundred or more individual cell modulessafely interconnected internally with no intermediate cell moduleelectrical terminations exposed between the battery module endterminations. A single battery module of the present invention can besafely built with multiple cell modules to have an output of 300 voltsor more. A further alternate or additional object of the presentinvention is to promote heat transfer from the individual cell modulesto the outside environment via the thermally-conducting,electrically-insulating peripheries of the cell modules and theirinterconnectors. Yet a further additional or alternate object of theinvention is to provide for ease of installation and assembly and/ordisassembly of a modular battery.

Cell Module

The cell module of the preferred embodiment of the present invention canhave a rigid or semi-rigid flat shape with a positive and a negativesurface on opposite sides which are in electrical communication withadjacent cell modules to form a higher voltage battery stack of cellmodules. Within each cell module there are arranged multiple positiveand negative electrodes, with each positive and negative electrodeelectrically connected in parallel to each of the other electrodes ofthe same polarity. The electrodes are made with any suitable lithium ionbattery material for the positive and negative electrodes. For example,the positive active material, or the cathode, may include lithiummanganese oxide, lithium cobalt oxide or lithium iron phosphateelectrochemically-active material coated onto aluminum The negativeactive material, or the anode, may include, for example, syntheticgraphite or lithium titanate spinel, coated onto copper (or aluminumwhere the anode is lithium titanate spinel).

The cell module incorporates multiple electrodes which, in theillustrated embodiments, have four patterns of active material coatingsas shown in FIGS. 1A-1D. FIG. 1A illustrates an interior positiveelectrode 9 (e.g., aluminum) that is coated on both sides with a cathodeactive material 1 and that has a bare (uncoated) foil tab 2 on one side,and FIG. 1B illustrates an interior negative electrode 10 (e.g., copperor aluminum) that is coated on both sides with an anode active material3 and that has a bare (uncoated) foil tab 4 on the opposite side to thepositive tab. FIG. 1C illustrates a positive end-electrode 14 that iscoated on one side only with a cathode active material 5 and that hasone or two bare foil tabs 6, and FIG. 1D illustrates a negativeend-electrode 15 that is coated on one side only with an anode activematerial 7 and that has one or two bare foil tabs 8. The advantage oftwo end plate tabs is to allow improved subsequent sealing of theelectrodes in the cell module. In this embodiment, the electrodes 9, 10,14, 15 are in the form of plates of rectangular shape, it beingunderstood that electrodes of other suitable forms and shapes can beused depending on the desired configuration of the cell module and otherdesign considerations.

Both sides of the end electrodes 14 and 15 that are at opposite ends ofthe assembled cell module may be uncoated and the surfaces cleaned andetched to achieve improved subsequent sealing to the cell module. Thecell module in the present invention preferably is well sealed fromwater vapor and air ingress.

In FIG. 2, the positive and negative electrodes (electrode plates) 9,10, 14, 15 illustrated in FIGS. 1A-1D are shown assembled within asingle cell module. In the drawings, the thickness of the activematerial coatings 1, 3, 5, 7 is greatly exaggerated for clarity. Thepositive and negative electrodes are electrically connected in parallelto multiple others of the same polarity to form an interleaved electrodeassembly which is terminated by the positive end-electrode 14 and thenegative end-electrode 15 of the single cell module. As illustrated inFIGS. 1C-1D and FIG. 2, the positive end-electrode plate 14 has two tabs6 and the negative end-electrode plate 15 has two tabs 8. One of thetabs 6 of the positive end-electrode plate 14 is connected, preferablyby welding, to the tabs 2 of the positive electrode plates 9 to form anend tab 12 which constitutes or is connected to a positive terminal ofthe cell module. In similar fashion, one of the tabs 8 of the negativeend-electrode plate 15 is connected, preferably by welding, to the tabs4 of the negative electrode plates 10 to form an end tab 13 whichconstitutes or is connected to a negative terminal of the cell module.Between the end-electrode plates 14, are positive electrodes 9interleaved with negative electrodes 10, and between each electrode is alayer of separator 11, with sufficient electrical insulating propertiessuch as a micro-porous polyolefin, containing electrolyte. In FIG. 2,the end-electrode plates 14 and 15 are shown coated on one side onlywhile their other sides are uncoated and through the end tabs 12 and 13respectively, their other sides present outer positive and negativecell-termination surfaces respectively for subsequent high voltagebattery assembly through the interconnectors of the present invention.

In actual practice, the number of electrodes and separator layers isvaried and selected to achieve the required electrochemical energystorage capacity and the power required. In addition to increasing theelectrochemical energy storage, a larger number of electrodes will allowhigher rates of charge and discharge for the same amount of energy. Thelarger surface area with multiple electrodes in the present inventionlowers the specific electrochemical current density per unit electrodearea within the cell module, i.e., the amperes per square centimeter ofelectrode is reduced for a larger number of electrodes so that theelectrodes can deliver more total current at a lower current densitywith less loss in delivery voltage. In batteries, high electrode currentdensity results in reduced battery voltage due to the well-knownelectrochemical principles of electrode polarization or voltage loss. Amultiple of more than 30 electrode pairs, in practice, could typicallybe bonded with a welder, such as an ultrasonic metal welder, into weldedend tabs 12 and 13 of the positive and negative electrodes,respectively. The electrode tabs are preferably connected along the fulllengths thereof on opposite sides of the electrode cell module, asillustrated by the end tab 12 on the positive side of the cell moduleand the end tab 13 on the negative side. The outside top surface of thecell module presents the bare foil surface of the positive end-electrode14 and the outside bottom surface presents the bare metal surface of thenegative end-electrode 15. Voltage and temperature sensors attached tothe individual tabs or to the electrode tabs provide early informationrelated to safety due to their close proximity to the electrode activematerials, and such sensors may be connected to a control system.

The sealing of the interleaved electrode assembly of FIG. 2 isillustrated in FIG. 3A with the positive and negative active materialsshown in cross section for each electrode. As noted above, theend-electrode plates 14, 15 have two tabs and are coated with activematerial on only one side. Each of the positive and negative end tabs 12and 13 is sealed with an electrically insulating sealant 16 at theopposite edges of the cell module 23 and electrically isolated one fromthe other by an insulator 17 where the opposite polarity tabs overlap onthe same side as illustrated in FIG. 3A. The sealant 16 may also bethermally conducting in order to remove heat from the cell module. Moreparticularly, the insulator 17 on the left side of the cell module 23electrically isolates the tab 8 of the negative end-electrode 15 fromthe positive end tab 12, and the insulator 17 on the right sideelectrically isolates the tab 6 of the positive end-electrode 14 fromthe negative end tab 13. Also in FIG. 3A is shown a gap 18 between thesealant 16 and the ends of the electrodes 9, 10 and the separators 11.The material of the sealant 16 may also seal a plastic frame 19 (FIG. 5)to the interleaved electrode assembly on each of the sides orthogonal tothe sealed end tabs 12 and 13. Methods of sealing includeinsert-molding, injection molding, fusion welding and adhesive (bothreactive, e.g., epoxy, and hot-melt).

As shown in FIGS. 4 and 5, the plastic frame 19 is a two-partelectrically insulating frame having front and rear, generally C-shaped,frame sections 19 a, 19 b that are inserted over the interleavedelectrode assembly and the sealant 16 at the front and rear of the cellmodule 23 and sealed thereto. The plastic frame 19 may also be thermallyconducting in order to remove heat from the cell module. FIG. 3A showsthe cell module 23 without the frame 19 a, and FIG. 3B shows the cellmodule 23 with the front frame section 19 a sealed to the cell module.FIG. 3B illustrates features incorporated in the frame 19 a including aport 20 for evacuating, filling and draining the cell module withelectrolyte which can also be permanently or temporarily sealed bymechanical means, electrical feedthroughs 21 for measuring andmonitoring individual cell voltages and temperatures, and a burst disc22 to relieve any pressure build up within the cell module 23.

In order to electrically connect stacked cell modules 23 in series,electrically conductive compressible interconnectors 24 are interposedbetween adjacent cell modules. FIG. 3 shows upper and lowerinterconnectors 24 for series connection to additional cell modulesabove and below the illustrated cell module 23. FIG. 4 is a top planview of the sealed cell module 23 with the upper interconnector 24included and the outside surface (bare foil surface) of the negativeend-electrode 15 of the cell module in contact with the lowerinterconnector 24. The interconnectors as illustrated in FIGS. 3 and 4in the present invention do not extend beyond the periphery of the cellmodule in order to protect against electrical arcing or shock shouldcontact be made with the periphery during interconnection of multiplecell modules during assembly of the battery module of the presentinvention. Protection against electrical arcing or shock on peripheralcontact, could also be accomplished by electrically insulating the sideperipheries of the electrically-conducting interconnector materials.

As illustrated in FIGS. 2 and 3A, the tabs 2, 4, 6, 8 of the electrodeplates are shown sharply bent at an angle to overlap one another to formthe end tabs 12, 13. It is of course possible, and sometimes preferable,to bend the tabs with a curvature rather than the sharp bending shown.Also, as illustrated in FIGS. 1C and 1D, the widths of the tabs 6 and 8of the end-electrode plates 14, 15 could be different on opposite sides(left/right sides) of the end-electrode plates, the wider width tabsbeing connected to the end tabs or terminals 12, 13 and the narrowerwidth tabs sitting on the insulators 17. The ports 20 are preferablyplaced on diagonal corners for subsequently filling and vacuum degassingthe cell module after formation.

In this embodiment, as shown in FIGS. 2, 3A and 3B, voltage sensors 30 aare attached to both the positive end tab 12 and the negative end tab13, which permit monitoring the voltage of any cell within a batterystack of cell modules and adjusting its state of charge to balance cellswithin a multi-cell-module battery through an external batterymanagement system (BMS). Temperature sensors 31 a, such as thermistors,are mounted in contact with both the positive end tab 12 and thenegative end tab 13 to monitor the temperature of the electrodes of thecell module 23. The voltage sensors 30 a and the temperature sensors 31a are electrically connected by sense lines (conductors) 30 b and 31 b,respectively, to the electrical feedthroughs 21 provided in the frontand rear frame sections 19 a, 19 b, as illustrated in FIG. 5. The cellmodule 23 is furnished with the burst disc 22 to relieve excess internalpressure in the event of a catastrophic cell failure.

The complete cell module 23 is intended as a manufacturing module thatmay be handled in a dry-room, dry-box or other controlled environmentthroughout cell formation and vacuum degassing. In addition tomeasurement of the individual cell module voltages, the voltage sensorsmay also be used to measure any resistive component between the cellmodules, for example, arising at the mechanical contacts between theinterconnector 24 and the positive end-electrode 14 of one cell moduleand between the interconnector 24 and the negative end-electrode 15 ofan adjacent cell module. As discussed herein, although use of an inertgas in the vicinity of the interconnector electrical contacts isdesirable to prevent or reduce the development of anelectrically-resistive layer between the interconnector and the cellmodule electrical surface contact, the capability to continuouslymonitor the electrical resistivity of such mechanical contacts is anadditional benefit and feature of the present invention.

In an automated assembly process, or in mass manufacturing, all foursides of the interleaved electrode assembly may be sealed into theplastic frame 19 in a single step while simultaneously incorporatingfill holes, burstable areas and embedded sensor wiring in the same orsubsequent refinement steps. In an automated manufacturing process, theplastic frame may be eliminated entirely by, for example, use ofinjection molding in which the interleaved electrode assembly of FIG. 2is placed between top and bottom molds each in contact with the otherand enclosing an open continuous perimeter volume into which anelectronically-insulating polymeric sealing material is injected to makea continuous cell module perimeter seal incorporating perhapsprior-positioned fill tubes, sensors and thin areas for burstprotection.

Interconnector

The present invention provides interconnectors 24, shown for Example inFIG. 6A, which advantageously can be compressible to provide cushioningfor shocks or vibrations between the planar cell modules 23. Theinterconnectors 24 for example can be compressible flexible conductivesheets that provide a multiplicity of parallel conduction paths. Theflexibility of the interconnectors 24 can accommodate cyclic strainswithin the cell stack during charging and discharging the battery, whilemaintaining electrical contact between the cell plane modules throughapplication of a force that assures good contact and low electricalresistance between the modules. The compressible interconnectors 24 canbe made of any material that has sufficient properties such as, forexample a wire mesh, metal or carbon fibers or strips retained in acompressible elastomeric matrix or non-woven pad, or an interwovenconducting mat, consistent with the requirement for a compressibleflexible electrically-conducting interconnection between adjacent cellplate module surfaces. The contacting surfaces of the cell modules canbe chosen to maintain a long-term, low-resistance connection interfacewith the surfaces of the positive and negative connections of the cellmodule.

The mesh for example can be of filaments of approximately 4 mils, or0.004 inches. The compressibility of the interconnector can be forexample 30 percent, so that for example upon application of sufficientforce to reduce spacings in the weave, the volume of the interconnectdecreases to 70 percent of the volume prior to application of force.Thus an interconnect layer having a thickness of 10 mils can compress toa thickness of 7 mils upon pressure on the planar surfaces, given alayer structure in which during this compression the layer does notexpand out of the sides perpendicular to the pressure direction.Preferably, the compressibility of the interconnector is such that thevolume can compress to less than 90 percent.

In addition, certain interconnectors of the present inventionadvantageously can improve the conductivity of the cell moduleconnection, as opposed to the prior art using direct metal-to-metalcontact between adjacent cells or the use of conducting cements orpastes between adjacent cells. Table 1 shows various materials that wereused to make compressible weaves or felts of interconnector material inaccordance with the present invention. Some of the fibers had a surfacefinish to improve stability of the contact material of theinterconnector.

TABLE 1 Materials Used for Interconnected Pads of the Present InventionThickness Pad Weight Material Fiber Surface Finish Inch gram/in2 Acopper/steel Tin 0.020 0.33 wire B monel None 0.020 0.31 wire C aluminumNone 0.021 0.10 wire D nylon Silver 0.072 0.24 felt E woven Silver 0.0150.08 nylon F carbon Nickel 0.018 0.25 fiber G non-woven Copper 0.0120.04 polyester H non-woven Nickel 0.014 0.17 polyester

Interconnectors in the form of one inch square pads of material madefrom the materials illustrated in Table 1 were placed between pressureplates surfaced with metal foils of Al or copper (Al and Cu simulate theouter surfaces of the example Li ion cell modules of the presentinvention) and the electrical resistance was measured on application ofelectrical current and mechanical pressure to the interconnector padsvia the pressure plates with Al or Cu foil surfaces. The resultingelectrical resistances measured under the same conditions and for thesame areas of interconnector are shown in Table 2. The pressure appliedwas approximately 10 pounds per square inch.

TABLE 2 Electrical Resistance Values for Interconnection between Al andCu Surfaces Interconnection Lower Upper Resistance Foil FoilInterconnector (milliohms) aluminum aluminum None 35 copper aluminumNone 3.0 aluminum aluminum A <1 aluminum aluminum B 2.5 aluminumaluminum C 37 aluminum aluminum D 5.1 aluminum aluminum E 2.8 aluminumaluminum F 18 aluminum aluminum G 2.8 aluminum aluminum H 127 copperaluminum A <1 copper aluminum B 3.0 copper aluminum Conducting 40 SilverCement copper aluminum Conducting 130 Graphitic Cement copper aluminumConducting Paste 2.6

Interconnector A for example is a preferred embodiment of theinterconnector of the present invention, and may for example be madefrom electromagnetic interference/radio frequency interference shieldingproducts such as gaskets available from the MAJR Products Corporation ofSaegertown, Pa.

Several of the interconnectors 24 of the present invention, in additionto reducing shock and vibrations, for example from road shock, canimprove or maintain electrical resistance. Continuity in current flowbetween interconnected cell modules in the presence of vibrations isalso an important safety and reliability feature for the vehicle becauseif there were a diminution or a single point break in continuity ofcurrent flow, reduced or no power output from the battery could beobtained since a single point break or diminution in current flowbetween any pair of cell modules in any modular battery would also“disconnect” or diminish current flow respectively for all of the otherseries-connected cell modules from power delivery for the vehicle, whichessentially immobilizes the entire vehicle. This could also become avehicle safety issue in an emergency situation where the vehicle mustavoid a road accident for instance. The use of compressible springyinterconnectors in accordance with the present invention can avoid theoccurrence and effects of a “single point failure” or diminution ofcurrent flow and sharply contrasts with the use of conductive cementsand pastes in the prior art which may not be capable of withstandingexcessive vibrations or continual road shocks without physicallybreaking or changing electrical connectivity and current continuity.

The interconnectors also have the advantage of being removable to permiteasy removal of the cell modules and replacement of defective cellmodules.

The interconnectors preferably are used between aluminum-aluminum oraluminum-copper end electrodes of a cell module, and preferably includenickel, tin, silver or copper, and most preferably copper or silver. Toimprove and maintain the interface connection, the surfaces of theinterconnectors 24 may for example be surface treated, such as by tinplating or indium plating.

To illustrate the advantages of the present invention in absorbingvibrations (pressure changes) without change of electrical resistance,Table 3 shows the effect of pressure on the electrical resistance of thecompressible interconnector of the present invention at differentapplied pressures. Increase in the pressure applied to a one inch squarepad of interconnect material A (Table 1) produced no further reductionin electrical resistance above an applied pressure of 15 pounds persquare inch (psi).

TABLE 3 Electrical Resistance Values for Interconnection Material Abetween Al and Cu Surfaces Pressure (psi) applied to interconnectorInterconnection pad (A) between Cu and Al Foils Resistance (milliohms) 00.19 10 0.06 15 0.01 20 0.01

Modular Battery

FIGS. 6A and 6C illustrate how multiple cell modules can be arrangedelectrically in series to form a battery stack to provide a high-voltageand high-power modular battery while also protecting against electricalarcing and shock on peripheral contact during assembly of themulti-celled high voltage battery. FIG. 6A shows six cell modulesstacked one on another electrically in series and separated by thecompressible interconnectors 24 of the present invention which serve toelectrically connect in series one cell module to the next cell moduleand which are not electrically in contact with the edge periphery of thestack of cell modules or the wall of the battery module housing orenclosure. It is noted that several interconnectors can be presentbetween two cell modules, for example 8 layers, each 10 mils inthickness. Thus the space between cell modules for example can be 80mils, and compressible to 60 mils when in use.

By way of example and as described above, the positive cell modulesurface may be made of aluminum and the negative cell module surfacemade of copper. As shown in FIG. 6A the interconnectors 24 do not extendbeyond the side peripheries of the cell modules and so do notelectrically contact the inner walls of the battery enclosure, whilesimultaneously maintaining electrical isolation from otherinterconnectors within the stack of cell modules. Electrical insulationof the side peripheries of the interconnectors 24 may be achieved by thegas, for example inert gas, filled space enclosed by the sideperipheries of the interconnectors 24 and the cell modules 23 and theinner walls of the enclosure. Electrical insulation could also beachieved by application of an electrical insulator to the sideperipheries of the interconnectors as shown by sealant or a gasket 35 inFIG. 6C.

In the illustrative example in FIG. 6A, six cell modules 23 arecontained in a stacked array within an enclosure 25 which, in thisembodiment, is of rectangular cross section. The enclosure 25 is ahermetically-sealed case, which for example may be made from aluminum,preferably either fabricated from sheet metal or made of castconstruction. To permit stacking and assembly of the cell modules 23,and removal and replacement of individual cell modules after assembly,the top or bottom, or one of the sides, of the enclosure 25 isdetachably connected to the enclosure by threaded bolts or othersuitable fasteners. The enclosure 25 provides the ability to locate thecell modules and interconnectors in a stack in a robust mechanicalconfiguration that withstands shock and vibration in the batteryoperating environment and if electrically conducting also serves as thenegative connection for power to and from the battery. In FIG. 6A, sixcell modules are shown for illustrative purposes, whereas a practicalbattery may accommodate from 10 to 100 cell modules or more. The presentinvention allows a large number of cell modules to be interconnected tomake a very high-voltage battery stack preferably the number of cells isat least 50 and the voltage at least 150 Volts.

The sides of the enclosure 25 in FIG. 6A may be thermally but notelectrically in contact with the interconnectors 24 to facilitate heattransfer to the outside environment by adding thermally conductive butelectrically insulating material to the side periphery of theinterconnectors as illustrated in FIG. 6C, via for example a sealant orgasket 35. Examples of thermally conductive but electrically insulatingmaterials for elements 16, 19, 35 of the present invention includefilled polymers. At least two, but even all four sides of the enclosure25 are in thermal contact only with the side peripheral edges of thecell modules 23 and interconnectors 24 to maximize heat transfer to theoutside environment. Thermal contact between the cell modules 23 and thewalls of the enclosure 25 is furnished by a layer of thermallyconductive but electrically insulating material 25 a, such as forexample an electrically-insulating coating from hard anodizing of analuminum enclosure on the interior of the enclosure, in addition anelastomeric electrically-insulating and thermally-conducting gasket 35around the side peripheral edge of each interconnector, may also beincluded to further improve heat removal although any material withsuitable thermally-conductive and electrically-insulating propertiescould be used. Heat dissipation from the cell modules may be furtherenhanced by adding fins to the exterior of the enclosure (therebyimproving convective heat-transfer), and by back-filling the interiorvolume of the enclosure with helium gas (thereby improving conductiveheat transfer). Filling the enclosure with an inert gas also reduces thepotential for undesirable metal oxidation which may increase theelectrical resistance of the interconnection points between theinterconnectors and the external surfaces of the cell modules. Aluminumis particularly susceptible to such oxidation in the presence of air andcan form a hard electrically-resistive oxide film.

Selection of electrode active materials that undergo thermodynamiccooling on charge or discharge is also advantageous in reducing heatgeneration and temperature rise in a battery since on discharge Ohmicheating occurs proportional to the square of the discharge current(i²R). Ohmic heating can be counteracted by the thermodynamic cooling toreduce the rate of temperature rise on charging or discharging.

The enclosure 25 incorporates feedthroughs for the power input andoutput terminals, namely, a positive terminal 26 and a negative terminal27. The power terminals connect internally to the ends of the cellmodule battery stack through an internal power bus 28 for the positiveterminal 26 and the electrically conductive enclosure 25 serves as thenegative bus 29 to the negative terminal 27. The terminals 26 and 27 areelectrically insulated one from the other by for example at least oneelectrically-insulated feedthrough from the bus to the terminal of thesame polarity. The enclosure 25 is provided with external multipinconnectors 30 and 31 for monitoring cell voltage and cell temperature,respectively, and these connectors may be positioned in the same regionas the power terminals 26 and 27. In the illustrated embodiment, thereare six sets of multipin connectors 30 and 31 (FIG. 6B), one set foreach cell module 23. The sense lines 30 b and 31 b of each cell moduleare connected via the electrical feedthroughs 21 to sense lines 30 c and31 c which, in turn, are connected to respective ones of the multipinconnectors 30 and 31. To facilitate removal and replacement ofindividual cell modules 23 from the stacked array, the sense lines 30 c,31 c may be connected to the feedthroughs 21 by pin-and-socketconnectors or other suitable connectors that permit easy attachment anddetachment. In FIG. 6A, the internal connections of the sense lines 30c, 31 c from the multipin connectors 30 and 31 to the cell modules 23are only shown for one cell module. In practice, connections could runto some or all cell modules in the battery stack. Data acquisition, asdiscussed above, from the individual sensors 30 a and 31 a is sent to astand-alone or an integrated analysis, control and communications modulewithin the overall vehicle system. An external pressure relief device 32may be provided to safely handle any high pressure failure modes of thebattery stack. The use of multipin connectors 30 and 31 in the presentinvention facilitates replacement of individual cell modules.

Although the present invention is illustrated herein with anelectrically conducting enclosure 25, it could also be made of anon-electrically-conducting material, in which case a separate negativebus 29 would connect the negative surface of the cell module 23 at theone end of the stack of cell modules 23 to the negative terminal 27 ofthe battery. An advantage for example of using a non-metallicelectrically insulating enclosure 25 could be lower cost and lighterweight. Use of heat-conducting material in the walls of the enclosure tofacilitate heat removal from the cell modules to the outside of theenclosure 25 would be advantageous as would be the use of active orpassive cooling means adjacent to the outside walls of the enclosure 25,for example, a heat absorbing material or flowing coolant in contactwith the outside walls of the enclosure would benefit heat dissipation.

For lower electrical resistance between cell modules 23 in the batterystack, pressure can be applied to the compressible interconnectors 24between the cell modules 23. An example of how this might be readilyachieved is shown in FIG. 6A where a spring 33 is located at the top ofthe enclosure 25 and positioned between the positive electrical bus 28and the top of the enclosure 25. Spring 33 transmits pressure to theinterconnectors 24 within the stack of cell modules 23. Additionally, oras an alternative, a spring may be incorporated at the bottom of theenclosure 25 to apply pressure from below to the stack of cell modules23 and interconnectors 24. The positive electrical bus 28 iselectrically insulated from the enclosure 25, for example by use of anelectrically insulated spring 33.

In FIG. 6A, the terminals 26 and 27 and the multipin connectors 30 and31 and the burst disc 32 and gas port 34 are illustrated as beingpositioned on the top surface of the enclosure 25, where the surface isparallel to the end electrodes 14 and 15. In accordance with the presentinvention, all of these elements could be positioned on one or moresides of the enclosure 25

The enclosure 25 provides the following features: a means of compressionof the stack of cell modules, a hermetically sealed enclosure, and ameans for electrical connection to the surfaces of the end cell modules.

During operation of the battery of the present invention, an electronicmanagement system may be provided to continuously monitor cell modulevoltages and cell module temperatures, as well as the voltage dropacross the interconnectors. Such extensive monitoring of batteryfunction with such close coupling of the sense points to cells, allowsfor improved battery monitoring and leads to improved battery safety. Asimple schematic data monitoring and alerting arrangement between acentral monitoring center and an HEV is shown in FIG. 7.

In FIG. 7, an HEV is equipped with a battery 40 comprised of multipleseries-connected cell modules constructed according to the presentinvention. The battery 40 is connected to a battery controller 48 whichmonitors and controls the battery performance in a manner known in theart. The battery controller 48 communicates with a central station 44through a wireless communications network which includes an antenna 45mounted on the HEV and a central station antenna 46. The batterycontroller 48 continuously monitors the voltage and temperature of eachcell module and, when necessary, reduces the current flow through one ormore cell modules to maintain the current at a safe level. The batterycontroller 48 transmits monitoring data to the central station 44 andreceives notification data from the central station to regulateoperation of the battery 40.

Charge transfer through the voltage sense leads may be used to keep theelectrochemical capacity of the cells in balance. High-voltage and/orhigh temperature indications would trigger the battery management systemto take corrective action, such as disconnecting the battery from itscharging source—an important safety feature particularly for HEVapplications. Drift of parameters over time could be an indicator forrequired maintenance. The battery of the present invention with itsseparable connections between cell modules readily permitselectrically-safe battery disassembly and replacement of defectivecomponents, greatly extending the service life of the entire batterybuilt in the inventive manner.

The use of planar or flat electrodes in the cell module of the presentinvention allows thicker coatings of positive and negative material tobe used on the electrode plates than can be practically used withelectrodes which have to be bent to make, for example, a cylindricalcell in which the electrodes are bent to form a spiral, which is acommon method of construction of many battery cells. There arelimitations to the thicknesses of coatings on electrodes that have to bebent into a spiral form for cylindrical cells, because bending of anelectrode with a thick coating of active material can cause stresswithin the thick coating which can result in cracking of the activematerial and subsequent loss of direct electrical contact to thesupporting and conducting surface which, in turn, would reduce theusable Ampere-hour (Ah) capacity particularly at high electricalcurrents. A significant increase in the available Ah capacity of a cellmodule of the present invention can be achieved with the use of planaror flat electrodes with thicker coatings of the active materials andsuch increase in capacity would be attained with an increase in thespecific energy density (Watt-hours per unit weight or volume) becauseof the relative increase in the ratio of weight and volume of the activematerial to the weight and volume of the inactive materials of theelectrode, principally the active material supporting structures (forexample the copper and aluminum active material supports of the examplesgiven herein)

Although the electrodes in the illustrated embodiments are disclosed aspreferably having a square or rectangular planar form, other planarforms can be made in accordance with the present invention. For example,a cell module of the present invention can also be of cylindrical foamby, for example, cutting the positive and negative electrodes into theform of planar discs and interleaving them with a separator in an offsetmanner to allow for subsequent welding together of all the positiveelectrode planar discs and separately all of the negative electrodeplanar discs. The perimeter sealing of the welded stack of interleavedelectrodes with sensing and filling feedthroughs could be accomplishedusing a curved frame, for example, semicircular. The resulting cellmodules would resemble in appearance thick discs or flattened cylinderswhich would then be stacked on one another and electrically connectedwith the interconnectors of the present invention and subsequentlysealed into an enclosure to make a cylindrical multicell battery with apositive end surface disc and a negative end surface disc. Theflexibility in shape, size and form factors of the cell module of thepresent invention enables maximum utilization of available space withinan application requiring a battery and enable flexible customizablemanufacturing of cell modules.

While the invention herein described is illustrated with particularreference to a lithium battery, other battery chemistries would benefitfrom the invention. In particular, batteries requiring very high ratesof charge and discharge as in HEV applications would especially benefitdue to the large interconnection area between adjacent cell modules andthe large number of the positive and negative electrodes. Such a largeinterconnection area between adjacent cell modules which is madepossible with the present invention lowers the specific current density,i.e., the amperes per square centimeter, so that the electrodes candeliver more total current at a lower current density with less voltageloss for the cell module. In batteries, high current density on anelectrode results in reduced battery voltage due to the well knownelectrochemical principles of electrode polarization. The electricalinsulation of the side peripheries of the cell modules and the internalinterconnectors between the cell modules from electrical shock onexternal contact, allows high voltage batteries to be safely built,maintained and recycled.

Battery chemistries benefiting from the present invention include alllithium batteries, as well as Pb-acid, Ni-metal hydride, Ni—Zn, andother rechargeable as well as primary or non-rechargeable batteries.

It will be appreciated by those ordinarily skilled in the art thatobvious variations and changes can be made to the examples andembodiments described in the foregoing description without departingfrom the broad inventive concept thereof. It is understood, therefore,that this disclosure is not limited to the particular examples andembodiments disclosed, but is intended to cover all obviousmodifications thereof which are within the scope and the spirit of thedisclosure as defined by the appended claims.

1. A modular battery comprising: a housing, a first planar battery cellremovably inside the housing, the first planar battery cell includingfirst positive electrodes including cathode material but not anodematerial thereon, first negative electrodes including anode material butnot cathode material thereon and first insulators at side peripheries ofthe first planar battery cell, the cathode material and anode materialof the first planar battery cell being between the first insulators, thefirst insulators electrically insulating the first positive electrodesand the first negative electrodes from the housing, the first positiveelectrodes including at least one internal first positive electrode, thefirst negative electrodes including at least one internal first negativeelectrode; a second planar battery cell removably inside the housing,the second planar battery cell including second positive electrodesincluding cathode material but not anode material thereon, secondnegative electrodes including anode material but not anode materialthereon and second insulators at side peripheries of the second planarbattery cell, the cathode material and anode material of the secondplanar battery cell being between the insulators, the second insulatorselectrically insulating the second positive electrodes and the secondnegative electrodes from the housing; and an interconnector removablyinside the housing disposed between the first planar battery cell andthe second planar battery cell parallel to the cathode material and theanode material of the first and second planar battery cells, theinterconnector electrically connecting the first and second planarbattery cells; wherein the first insulators include a positive firstinsulator at a first end of the first planar battery cell and a negativefirst insulator at a second end of the first planar battery cellopposite the first end of the first planar battery cell, the at leastone internal first positive electrode including the cathode material ata first end thereof and a bare tab at a second end thereof opposite thefirst end, the bare tab of the at least one internal first positiveelectrode being surrounded by the positive first insulator, the at leastone internal first negative electrode including the anode material at afirst end thereof and a bare tab at a second end thereof opposite thefirst end, the bare tab of the at least one internal first negativeelectrode being surrounded by the negative first insulator.
 2. Themodular battery as recited in claim 1 wherein the first positiveelectrodes include a first positive end electrode including cathodematerial on only one side thereof, the at least one internal firstpositive electrode including cathode material on both sides thereof. 3.The modular battery as recited in claim 2 wherein a side of the firstpositive end electrode opposite the side including cathode materialcontacts the interconnector.
 4. The modular battery as recited in claim3 wherein the second negative electrodes include a first second negativeend electrode including anode material on only one side thereof and atleast one internal second negative electrode including anode material onboth sides thereof.
 5. The modular battery as recited in claim 4 whereina side of the second negative end electrode opposite the side includinganode material contacts the interconnector such that the interconnectoris sandwiched between the first positive end electrode and the secondnegative end electrode.
 6. The modular battery as recited in claim 1wherein the first negative electrodes include a first negative endelectrode including anode material on only one side thereof, the atleast one internal first negative electrode including anode material onboth sides thereof.
 7. The modular battery as recited in claim 1 whereinthe first and second insulators are made of a thermally conductivesealant.
 8. The modular battery as recited in claim 1 wherein the firstinsulators include a first positive insulator and a first negativeinsulator, the first positive electrodes being are coupled together inthe first positive first insulator, the first negative electrodes beingcoupled together in the first negative first insulator.
 9. A modularbattery comprising: a housing, a first planar battery cell removablyinside the housing, the first planar battery cell including firstcathodes, first anodes, a first cathode sealant sealing the firstcathodes from a first side of the housing and a first anode sealantsealing the first anodes from a second side of the housing opposite thefirst side, the first cathodes extending into the first cathode sealant,the first anodes extending into the first anode sealant; a second planarbattery cell removably inside the housing, the second planar batterycell including second cathodes, second anodes, a second cathode sealantsealing the second cathodes from the first side of the housing and asecond anode sealant sealing the second anodes from the second side ofthe housing opposite the first side, the second cathodes extending intothe second cathode sealant, the second anodes extending into the secondanode sealant; and an interconnector removably inside the housingdisposed between the first planar battery cell and the second planarbattery cell and electrically connecting the first and second planarbattery cells, peripheries of the interconnector being electricallyisolated from the first and second sides of the housing.
 10. The modularbattery as recited in claim 9 wherein the first cathodes include atleast one first internal cathode and the first anodes include at leastone internal anode, each of the at least one first internal cathodebeing formed of a plate having active cathode material on both sidesthereof, each of the at least one first internal anodes being formed ofa plate having active anode material on both sides thereof.
 11. Themodular battery as recited in claim 9 wherein the first anodes include afirst end anode and the second cathodes include a second end cathode,the first end anode including an active anode material coated surfacefacing an inside of the first planar battery cell and a first baresurface facing the interconnector, the second end cathode including anactive cathode material coating surface facing an inside of the secondplanar battery cell and a second bare surface facing the interconnector.12. The modular battery as recited in claim 11 wherein theinterconnector contacts the first and second bare surfaces toelectrically connect the first anodes and the second cathodes.
 13. Themodular battery as recited in claim 9 wherein the first cathode sealantand the first anode sealant conduct heat from the first planar batterycell to the housing and the second cathode sealant and the second anodesealant conduct heat from the second planar battery cell to the housing.14. A method for forming a modular battery comprising: forming a firstplanar battery cell to include first positive electrodes each includingcathode material but not anode material thereon, first negativeelectrodes each including anode material but not cathode materialthereon and first insulators at side peripheries of the first planarbattery cell; forming a second planar battery cell to include secondpositive electrodes each including cathode material but not anodematerial thereon, second negative electrodes each including anodematerial but not cathode material thereon and second insulators at sideperipheries of the second planar battery cell; placing the first planarbattery cell in a housing so the first insulators insulate the firstpositive electrodes and the first negative electrodes from the housing;placing an interconnector over the first planar battery cell in thehousing such that the interconnector is positioned parallel to thecathode material and anode material of the first planar battery and theinterconnector does not extend past the side peripheries of the firstplanar battery cell; and placing the second planar battery cell in thehousing so the second insulators insulate the second positive electrodesand the second negative electrodes from the housing and so theinterconnector electrically connects the first and second planar batterycells; wherein the first positive electrodes are formed to each includea tab extending away from the cathode material, the first negativeelectrodes are formed to each include a tab extending away from theanode material, the first insulators include a positive first insulatorat a first end of the first planar battery cell and a negative firstinsulator at a second end of the first planar battery cell opposite thefirst end of the first planar battery cell, the tabs of the firstpositive electrodes extending into the positive first insulator, thetabs of the first negative electrodes extending into the negative firstinsulator.
 15. The method as recited in claim 14 wherein after the firstplanar battery, the interconnector and the second planar battery areplaced in the housing and the interconnector electrically connects thefirst and second planar battery cells, the interconnector is notelectrically in contact with side peripheries of the first and secondbattery cells or the housing.
 16. The modular battery as recited inclaim 1 wherein the first planar battery cell includes an electricallyinsulating frame on sides of the first planar battery cell orthogonal tothe first insulators.
 17. The modular battery as recited in claim 16wherein the electrically insulating frame is a two-part electricallyinsulating frame having front and rear, generally C-shaped, framesections inserted over the first positive and negative electrodes andthe first insulators.
 18. The modular battery as recited in claim 16wherein the electrically insulating frame is thermally conducting inorder to remove heat from the first planar battery cell.